This invention relates to physiological measuring instruments and in particular to an athlete's instrument for measuring body temperature and heart beats and computing pulse rate, distance traveled and velocity as a function thereof.
Instruments for measuring physiological parameters such as heart rate are known in the art. Standard electrocardiogram (EKG) devices are used to sense heart beats and generate an output electrical signal indicative thereof. The outputs generated by EKG's are useful in determining the physiological condition of the subject and particularly in detecting irregularities and/or potential problems in the cardiovascular system.
The number of individuals participating in vigorous athletic activity has been increasing in recent years. During physical exercise, the body requires greater supplies of oxygen and blood flow to meet the increased physical demands. This creates a greater load on the heart and results in increased heart rate, i.e. the number of heart beats in a given time. Overexertion of the heart during exercise can of course lead to adverse physiological effects, but one must reach a certain level of exertion to derive benefit from physical exercise.
Several devices are currently available for monitoring pulse rate activity. One such device is described in U.S. Pat. No. 3,792,700 wherein the pulse rate is measured by placing EKG electrodes under the armpits of the subject. This is well-suited to provide the pulse rate of a sedentary user, but is too cumbersome to be used by one engaged in athletic activity. U.S. Pat. No. 3,902,698 incorporates a pulse rate measuring device with a stationary exercise control system which generates a signal when a particular pulse rate is reached. U.S. Pat. Nos. 3,742,937, 3,807,388 and 3,863,626 describe miniature pulse monitoring devices which can be worn by persons engaged in physical exercise to indicate when a predetermined pulse rate has been exceeded. U.S. Pat. No. 3,978,249 describes a pulse rate indicator which measures both the at rest pulse rate and the pulse rate during physical exercise and generates a comparison signal based on the difference therebetween. When the difference exceeds a predetermined value, an alarm is activated to warn the user that he is overexerting. The device includes a display to indicate changes in the pulse rate activity.
In addition to pulse rate activity, the inner body or "core" temperature of an individual is also a significant factor in assessing the amount of work performed by the body and overall physical stress. Athletes engaged in strenuous exercise, particularly in hot weather, are susceptible to adverse effects such as heat stroke when the core temperature rises to 104.degree. F. As the body performs work, such as during prolonged exercise, the core temperature increases, which in turn causes the heart to beat faster. Thermometers and other temperature measuring devices known in the art must be inserted in a body cavity such as the mouth, armpit or rectal opening to accurately measure core temperature and are not practical for continuous monitoring of the body temperature.
A key parameter for an athlete such as a runner, swimmer, or bicycler, is the distance traveled in a given amount of time. Prior art methods for measuring distance traveled have involved attaching an inertial sensor to the runner to count the number of strides taken and calculate distance based on a predetermined stride length. Inaccuracies often result, however, because the stride length varies depending on a number of physical and psychological factors such as, for example, body weight, body temperature and general physical and mental states. The greater the distance and velocity at which the distance is traversed the greater the work that is performed by the body. Since the total number of heart beats and heart rate achieved are functions of the amount of work and the work rate performed by the body, the distance traveled in a given amount of time and the velocity can also be expressed as functions of the heart rate and the total number of heart beats during exercise.